Patent Document 1 (Unexamined Japanese Patent Application Publication No. 2003-207636) proposes a wave plate that can be used in common for two light fluxes each having a different wavelength, through form birefringence. According to this Patent Document 1, this wave plate is formed through a microscopic periodic structure whose size is a half or less of a wavelength of a target light flux, and the wave plate has the form birefringence that changes the state of polarization of two light fluxes each having a different wavelength, thereby, a wave plate capable of coping with two wavelengths such as, for example, 405 nm and 660 nm can be realized. The microscopic periodic structure whose structural period is 200 nm, duty ratio is 0.64 and structural height is 6000 nm is described in the example in the Patent Document 1.